It is already known to produce mini-transformers which are wholly potted, where the entire iron core including coils is surrounded on the outside by a plastic housing. A hardenable plastic is filled in from an open housing side, so that the transformer is completely surrounded by plastic up to the rim of the housing. However, the fact that a relatively large amount of plastic is needed is a disadvantage, as is the cumbersome and slow production method, because two-component plastics, which are suited for this purpose, harden only slowly over a period of hours. A further disadvantage lies in the poor way heat is conducted away, because the plastic layer surrounds the iron core on all sides.